Leviticus 18:18 forbids an Israelite man from taking a second wife who is her sister while the first sister is still alive. The verse is part of God’s instructions to Israel through Moses, and it protects the family and the marriage covenant from a practice that would bring rivalry, confusion and betrayal into the household.
“‘You shall not take a wife in addition to her sister, to be a rival, to uncover her nakedness, while her sister is still alive.
Leviticus 18:18 (WEB)
What Leviticus 18:18 Means
The verse begins with the instruction “You shall not take a wife in addition to her sister.” The phrase “in addition to” means taking a second wife alongside the first, and the sister relationship makes this especially painful. Two women who are sisters would share a home, a husband and very likely a bond of family loyalty that could easily turn into competition.
The verse then gives the reason: the marriage must not become “a rival.” The sisters should not be set against each other. The phrase “to uncover her nakedness” is a biblical idiom for sexual relations, so the verse is describing a marriage arrangement that God forbids. The clause “while her sister is still alive” makes clear the prohibition applies while the first sister lives. It does not describe what happens after a death, and it should not be stretched into a promise or a guarantee about any other situation.
The Context of Leviticus 18:18
Leviticus is one of the five books of the Torah, traditionally attributed to Moses and written for the people of Israel as they were shaped into a holy nation. Chapter 18 opens with a call to live differently from the surrounding nations of Egypt and Canaan. The chapter then lists a series of forbidden unions and sexual practices that protect the integrity of families and the holiness of the community.
The verses just before and after deal with close relatives: a daughter-in-law, a brother’s wife, a woman and her daughter, and a neighbor’s wife. Read this way, verse 18 belongs to a pattern in which God guards the family from confusion, favoritism and betrayal. Seeing that pattern helps the reader understand that the verse is less about a single arrangement and more about God’s care for the whole household.
Key Phrases in Leviticus 18:18
Matthew 19:6
So that they are no more two, but one flesh. What therefore God has joined together, don’t let man tear apart.”
(WEB)
Jesus affirms that marriage is a joining God has made, and that the two become one flesh. This helps explain why God guards the marriage covenant so carefully in the Torah, and why faithfulness within marriage matters so much.
Ephesians 5:25
Husbands, love your wives, even as Christ also loved the assembly, and gave himself up for it…
(WEB)
Paul calls husbands to love their wives with self-giving care. Read beside Leviticus 18:18, this shows that God’s concern for marriage is not only about what is forbidden but also about the kind of love that makes a household peaceful.
A Short Prayer From Leviticus 18:18
Lord, you know how easily our families can become places of comparison and hurt. Thank you that your law guards the bonds of marriage and family from rivalry and confusion. Help me to value the people you have placed in my life, and to refuse the jealousy that tries to set one against another. Give my marriage and my family the peace that comes from faithfulness to you. Amen.
